The present invention relates to an apicidin-derivative, a method of synthesis therefore, and an anti-tumor composition containing the same.
Histone is a basic protein bonded to DNA in a nucleus of a eukaryotic cell. Nucleosomal core histones undergo reversible acetylation at the amino group of specific lysine residues located in their N-terminal tails. Reversible acetylation of histone is supposed to mediate changes in chromatin structure, which is important in the regulation of gene expression.
The level of acetylation of histone in cell is controlled by equilibrium between the activities of two specific enzymes, histone acetyltransferase and histone deacetylase. So far, it has been reported that inhibitors having various structures inhibit human histone deacetylase.
The inhibitors are classified according to their structure as follows:
1) butyrate having a structure of a fatty acidxe2x80x94See, Newmark, H. L. et al., Cancer Lett., 78:1-5 (1994);
2) tricostatin A, suberoylanilide hydroxamic acid (SAHA) and oxamplatin having a structure of a hydroxamic acidxe2x80x94See, Tsuji, Ni. et al., J. Antibiot (Tokyo), 29:1-6 (1976); Richon. V. M. et al., Proc. Natl. Acad. Sci. USA, 95:3003-3007 (1998); and Kim, Y. B. et al., Oncogene, 18:2461-2470 (1999);
3) trapoxin A having a cyclic tetrapeptide structure containing 2-amino-8-oxo-9,10-epoxy-decanoyl (AOE)xe2x80x94 See, Kijima, M. et al., J. Biol. Chem., 268:22429-22435 (1993);
4) FR901228 and apicidin having a cyclic tetrapeptide structure without containing AOE xe2x80x94See, Nakajima, H. et al., Exp. Cell. Res., 241:126-133 (1998); Darkin-Rattray, S. J. et al., Proc. Natl. Acad. Sci. USA, 93: 13143-13147, 1996); and
5) MS-27-275 having a benzamide structurexe2x80x94See, Saito, A. et al., Proc Natl. Acad. Sci. USA, 96:45924597 (1999).
These compounds are known to inhibit the histone deacetylase in human cells, growth of cancer cells, and growth of tumors in animal models. Among them, the only compound which has received clinical approval and has been widely used is butyrate. However, the butyrate compound should be used at a high concentration (in a level of mM) so as to inhibit the histone deacetylase, and has a tendency to activate enzymes other than the histone deacetylase. Thus, this compound cannot be said to be an ideal agent. Clinical researches for a compound of a different structure which can selectively inhibit histone deacetylase at a low concentration (in a level of xcexcM (micromolar)) are actively conducted. FR901228 is currently under clinical trial (phase I, National Cancer Institute).
Based on the above-described facts, the histone deacetylase inhibitors are believed to be highly probable candidates which can be developed as agents having inhibitory effects against growth of tumors. However, at the present, use of these inhibitors in preparation of anti-cancer agents and their functional mechanisms are still not known.
The present inventors synthesized various derivatives from apicidin as a core molecule and filed an application for patent as to three compounds, SD9801, SD9802, and SD9803, which are each capable of inhibiting effectively growth of cancer cells (Korean Application for Patent No. 1999-11883).
Thereafter, the present inventors steadily endeavored to conduct research on histone deacetylase and finally discovered an apicidin derivative having excellent inhibitory effect against histone deacetylase at a low concentration, detransforming activity, and also being able to specifically inhibit growth of cancer cells while showing substantially no toxicity to normal cells. The present invention is formed based on this discovery.
Therefore, it is an object of the present invention to provide an apicidin derivative having a low toxicity to normal cells, a method of synthesis therefore, and an anti-tumor composition containing the same.
The present invention relates to an apicidin derivative represented by the following formula 1: 
wherein:
R is chosen from semicarbazone, thiosemicarbazone, hydrazone, tert-butylhydrazone, phenylhydrazone, 2,4-dinitrophenylhydrazone, 4-methoxyphenylhydrazone, 3-methoxyphenylhydrazone, 4-nitrophenylhydrazone, benzylhydrazone, methanesulfonylhydrazone, benzenesulfonylhydrazone, 4-methylbenzenesulfonylhydrazone, benzoylhydrazone, 4-nitrobenzoylhydrazone, carbohydrazone, benzyloxime or acetoxime.
Also, the present invention relates to a method for producing an apicidin derivative of the formula 1 characterized by reacting apicidin represented by the following formula 2 with hydrazines, carbazides or amines in the presence of a base or acid, as shown in the following reaction scheme 1. 
Here, as a reaction solvent for the above reaction, alcohols such as methanol or ethanol; aromatic solvents such as benzene or toluene; tetrahydrofuran (THF); ether and the like may be preferably used. More preferably, methanol or ethanol may be used. The base which can be used in the above reaction is preferably triethylamine, pyridine, sodium acetate and the like, more preferably triethylamine or pyridine. The acid which can be used in the above reaction is preferably acetic acid, hydrochloric acid or sulfuric acid in a small amount, more preferably acetic acid. In addition, the reaction scheme may further comprise a separation process by subjecting the reaction mixture to a reduced pressure to remove the reaction solvent and separating further using a commonly known method.
Also, in another aspect of the present invention, there is provided a histone deacetylase inhibitor containing a compound of the formula 1.
In a further aspect of the present invention, there is provided an anti-tumor composition comprising a compound of the formula 1 as an active ingredient.
The anti-tumor composition comprising a compound of the formula 1 as an active ingredient according to the present invention may be combined with a pharmaceutically acceptable carrier and may be applied in a form of injection solution for parenteral administration, oral administration, a liquid formulation such as syrup or emulsion, solid formulation such as tablets, capsules, granules or powders, and a topical formulation such as ointments.
Examples of the carrier for oral administration may include preferably starch, mannitol, cellulose, water or ethyl alcohol. Examples of the carrier for injection may include preferably water, physiological saline or dextrose solution. The anti-tumor composition according to the present invention may be combined with a carrier in a ratio of 1:99 to 99:1 by weight respective to the active ingredient.
In a still further aspect of the present invention, there is provided a method for treating or preventing tumors comprising administrating a therapeutically effective amount of a compound of the formula 1.
In a still further aspect of the present invention, there is provided use of a compound of the formula 1 as an anti-tumor agent.